Hi. I'm Jon Jagger.
I help software teams improve their effectiveness.
I built cyber-dojo, the place teams practice programming.
I'm based in the UK.
I've worked in 22 countries.
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Pages

How to read water

is an excellent book by Tristan Gooley (isbn 978-1-473-61522-9).
As usual I'm going to quote from a few pages:

One of the universal truths of human observation is that we
see
more of what we expect to see and less of what we don't expect to see.
Much of my work is not about teaching people to see things that are hard to see,
but in showing them how to notice the things that hide in plain sight.

It did not take sailors long to work out that a ship that carries too much may
be vulnerable in heavy seas, but sailors were rarely the ones to make the
decision about how much cargo a ship could safely carry. The merchants making
the profit would have had a different view to the deckhand, especially if the
trader never set foot on the vessel. This led to a wrestle between greedy traders
and cautious captains that lasted centuries. The first attempts to regulate how
much a ship could carry go back over four thousand years to ancient Crete.
Samuel Plimsoll, a nineteenth-century English politician, realized that a low
freeboard height can present a problem, but he also appreciated that it becomes
the solution if we take a very keen interest in it. In other words,
we can tell if there is too much cargo in the boat by looking much more carefully
at how high the water rises up the side of the hull. And the easiest way to do
this is by drawing a ruler on the side of the ship, calibrated according to an
architect's or engineer's understanding of the boat. These lines, which became
known as Plimsoll Lines, were such a simple and brilliant success that they
became law and proliferated around the world.

From 1833, when the first tide tables were produced by the Admiralty, the
emphasis shifted from looking, thinking and understanding, to depending
on tables of others' measurements.

There is a stange truth in the profile of beaches: they have evolved in a physical
sense to be a near ideal shape to defend themselves against the onslaught of the sea.
This means that almost any attempt to engineer a 'solution' to what nature is trying
to achieve has as much chance of backfiring as working.

Many sailors use little pieces of fabric, nicknamed 'tell-tails', that are
tied to the sails and stays (the wires that give the mast stability), to offer
a constant visual
reminder of what the wind is doing.

Once the depth of the water is half the wavelength of the waves, it effectively
cramps the motion of the waves and it is this that slows them down.

There will be an alternating combination of quick water and much slower
water and this always happens in a certain way. The quick patches are knowns,
perhaps onomatopoeically, as 'riffles' and the slower areas are known as pools.
If there is no human tinkering with a river's flow, then there will be a
riffle-pool sequence for every stretch of river that is fives times its width.

It is typical for the water at the sides of a river to be
travelling at only a quarter of the speed of the water in
the centre. The river is being slowed by two things at its sides;
when it comes into contact with banks it is slowed by friction
and it is also slowed by the shallowing at the sides.

A stream is just a river you can step over.

Swell is the name of the waves that have enough energy to
travel beyond the area of wind.